Black artifacts in some rendered images of a text
It looks like a topology problem.  You can convert the text to a mesh (Alt +C) and try the following.
 - Recalculating the normals (enter edit mode, select all, Ctrl+N)
 - Check for non-manifold geometry (edit mode - vertex mode, make sure nothing is selected then Ctrl+Alt+Shift+M) 
 - Remove double vertices (edit mode, W - remove doubles)  

If you would prefer to keep the text object, go to the object modifiers tab in the properties window, then try the following:  


add a decimate modifier
set the type to planar